Triggering and W-Polarisation Studies with CMS at the LHC

Results from studies on the commissioning of the Global Calorimeter Trigger (GCT) of the CMS experiment are presented. Event-by-event comparisons of the hardware with a bit-level software emulation are used to achieve 100% agreement for all trigger quantities. In addition, a missing energy trigger based on jets is motivated using a simulation study, and consequently implemented and commissioned in the GCT. Furthermore, a templated-fit method for measuring the polarisation of W bosons at the LHC in the Helicity Frame is developed, and validated in simulation. An analysis of the first 3.2/pb of sqrt(s) = 7 TeV LHC data in the muon channel yields values of (fL − fR)+ = 0.347 ± 0.070, f0+ = 0.240 ± 0.176, and (fL − fR)− = 0.097 ± 0.088, f0− = 0.262 ± 0.196 for positive and negative charges respectively. The errors quoted are statistical. A preliminary systematic study is also presented.